sedimentary
Chert (Jasper/Flint variety)
Silicon dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5-7 (Mohs); Color: Brownish-tan with white quartz veining; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6
- Hardness
- 6
- Color
- Brownish-tan with white quartz veining
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Brownish-tan with white quartz veining; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments and limestone cavities. This specimen shows secondary silica infilling cracks.
Uses & applications
Historically used for stone tools and weapons (flintknapping); currently used for architectural gravel, lapidary tumbling, and jewelry.
Geological facts
This specimen shows distinctive quartz or calcite veins filling stress fractures, creating a spider-web pattern common in septarian-like nodules or weathered river stones.
Field identification & locations
Identify in the field by its hardness (will scratch glass), conchoidal fracture pattern, and waxy texture. Commonly found in riverbeds, glacial tills, and sedimentary basins.
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